This application claims the benefit of Korean Application No. 2002-18377, filed Apr. 4, 2002, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to microwave ovens, and more particularly to an apparatus and a method of controlling a microwave oven, which can cook foods under optimal cooking conditions regardless of surrounding humidity conditions by compensating for variation of cooking conditions due to the surrounding humidity conditions.
2. Description of the Related Art
Generally, when rice is cooked in a conventional microwave oven, a first heating is performed until rice water reaches a boiling point of 100xc2x0 C., and then a second heating is performed for a predetermined period of time after the rice water reaches the boiling point using an output power of a magnetron lower than that of the first heating.
The microwave oven is not equipped with a temperature sensor and thus, detects the boiling of the rice water using a detection value from a humidity sensor, which senses a humidity value of water vapor discharged from a cooking chamber so as to detect the boiling point of the rice water.
FIG. 1A is a waveform diagram showing a relationship between sensing voltages of a humidity sensor and time in the conventional microwave oven. FIG. 1B is a waveform diagram showing a relationship between output powers of a magnetron and time in the conventional microwave oven. FIG. 1C is a waveform diagram showing a relationship between boiling temperatures of water and time in the conventional microwave oven. As shown in FIG. 1A, at a beginning of heating food, the output power of the magnetron is maximized to rapidly heat the food, and then, the output power is gradually lowered while continuing to heat the food. If the rice water boils, rice continues to be heated using low output power suitable for steaming boiled rice, so the rice is cooked. Accordingly, the humidity value sensed by the humidity sensor is a constant value at the start of cooking, rapidly increasing when rice water reaches the boiling point, and gradually decreasing thereafter.
A sensing voltage graph of the humidity sensor, as shown in FIG. 1A, shows a variation of the humidity value. A reference value (T1 FACTOR) of the humidity sensor, corresponding to the boiling point (100xc2x0 C.) of the rice water, is estimated on a basis of sensing voltage values. Generally, the reference value is uniformly set at a value of, for example, 85% of a maximum voltage MAX of the sensing voltages on a basis of a normal surrounding humidity condition.
However, a sensor for sensing relative humidity, not absolute humidity, is mainly used as the humidity sensor due to problems such as cost, etc. Then, if the surrounding humidity condition of the microwave oven is lower than that of a normal state, that is, a dry state, such as during Winter, the maximum voltage MAX sensed by the humidity sensor is relatively increased. Therefore, the voltage at 85% of the maximum voltage does not reflect the boiling point of rice water. Consequently, the output power of the magnetron is decreased to output a low output power suitable for steaming the rice before the rice water boils, thus causing rice to be half-cooked.
Various objects and advantages of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a method of controlling a microwave oven to cook foods under optimal cooking conditions regardless of a surrounding humidity condition, by compensating for a variation of cooking conditions due to the surrounding humidity condition.
To achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: performing a first heating until detection values of a humidity sensor reach a reference value, wherein the humidity sensor senses humidity of water vapor discharged from a cooking chamber; performing a second heating, lower than the first heating, after the detection values reach the reference value using an output power from a magnetron; determining a surrounding humidity condition of the microwave oven; and resetting the reference value of the first heating so as to cook food appropriately
Further, to achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: performing a first heating until detection values of a humidity sensor reach a reference value, wherein the humidity sensor senses humidity of water vapor discharged from a cooking chamber; performing a second heating, lower than that of the first heating, for a set period of time after the detection values reach the reference value using an output power from a magnetron; determining a surrounding humidity condition of the microwave oven; and resetting a period of time for the second heating so as to cook food appropriately according to the determined humidity condition.
To achieve the above and other objects, the present invention provides a control method of a microwave oven, including: maximizing an output power; counting a first heating time; reading sensing voltages from a humidity sensor during the first heating time; comparing the sensing voltages sensed by the humidity sensor with each other to determine a maximum voltage; setting a first reference value at a predetermined voltage level from the maximum voltage; determining whether a current sensing voltage sensed by the humidity sensor has reached the first reference value; decreasing the output power to a low power; determining whether the current mode is in a dry mode or a normal mode; setting a preset time as a reference period of time for a second heating time corresponding to the counted heating time; outputting the low power for a predetermined period of time of the second heating time; increasing the output power of the microwave oven to perform a cooking operation after the predetermined period of time of the second heating time elapses; and stopping the cooking operation of the microwave oven after the second heating time has elapsed.
To achieve the above and other objects, the present invention provides an apparatus to control a microwave oven, including: a control unit counting a time from a start of heating to a time point when a first reference value is detected, comparing the counted heating time with a predicted heating time preset; and determining a current mode as a dry mode when the counted heating time is shorter than the predicted heating time.
To achieve the above and other objects, the present invention provides an apparatus to control a microwave oven, including: a control unit determining a surrounding humidity condition of the microwave oven, and compensating for a variation of heating time due to the surrounding humidity of the microwave oven according to seasons or areas in which the microwave oven is used to provide an optimal heating time enabling the microwave oven to optimally cook food, regardless of surrounding conditions.
To achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: counting a time from a start of heating to a time point when a first reference value is detected; comparing the counted heating time with a predicted heating time preset; and determining a current mode as a dry mode when the counted heating time is shorter than the predicted heating time.
To achieve the above and other objects, the present invention provides a method of controlling a microwave oven, including: determining a surrounding humidity condition of the microwave oven; and compensating for a variation of heating time due to the surrounding humidity of the microwave oven according to seasons or areas in which the microwave oven is used to provide an optimal heating time enabling the microwave oven to optimally cook food, regardless of surrounding conditions.
These together with other objects and advantages, which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout.